The present invention relates to an improved pivot shaft.
Due to the technological trait to miniaturize, there are many products that possess unprecedented achievements while requiring the same space or even less than their predecessors. Lap-top computers, for instance, are very powerful and perform functions within the same space as prior products. Accordingly, computer screens or monitors, for example, are incorporated into the covers of the computers for space-saving's sake, and subsequently the covers can be opened at a desired angle such that the screen can be viewed and operation can take place. However, these computers are not provided with any supporting structures, but only depend on pivot shafts to pivotally connect the covers and achieve a stationary position of the screen.
FIGS. 5 and 6 of the drawings show a conventional pivot shaft. It can be seen that the pivot shaft is constructed with a L-shaped holder (4) pivotally connected a shaft (40). The shaft (40) having a pair of symmetrical notches at one end for a sleeve (41) to pivotally connect therein. A spring (42), with multiple packed rings, having one end inserted into a notch of the holder (4) and another blocked by a outer edge (410) of the sleeve (41), is provided between the holder (4) and the sleeve (41). Under normal circumstances, the shaft (40), coupled to a cover, blockades its rotation by the outer edge (410) of the sleeve (41), and maintains an angle .theta. (see FIG. 6) from the horizontal level. The outer edge (410) of the sleeve (41) compresses one end of the spring (42) when the cover is closed and locked. After unlocking the cover, the outer edge (410) of the sleeve (41) pushed by the compressed spring (42), causing the cover to bounce back to its original position, angle .theta.. Afterwards, the shaft (40) can rotate to an angle by means of the frictional force produced between the multiple packed rings of the spring (42) and the shaft (40); therefore, the cover can be fixed.
However, the conventional pivot shaft referred to in FIGS. 5 and 6 bears some drawbacks in its structure. The spring merely provides the outer edge (410) of the sleeve (41) and the shaft (40), as well as the cover, with the necessary force to return back to its original position, .theta. angle. Furthermore, the shaft (40), fixed at any desired position, lies in the frictional force produced between the spring (42) and shaft (40). As a matter of fact, the spring (42) does not do much work in this application. Also, the frictional force will dwindle due to mechanical wear and consequently influence the function of the computer screen.
FIG. 7 of the drawings shows another conventional pivot shaft. It can be seen that this pivot shaft is constructed with a holder (5), a shaft (50), and a washer (51). The holder (5) has a hole for the shaft (50) to pass therethrough. The shaft (50) has a pair of symmetrical notches on one end to engage with the cover and another end passes through the hole of the holder (95). The washer (51) is provided a rough surface thereon to provide a frictional force when the shaft (50) rotates to a desired angle and fastened thereon. However, this kind of pivot shaft also shares a destined drawback, i.e., the washer (51) is too fragile to stably support the cover and screen thereon as well as too weak to resist wear.
It is the purpose of this present invention, therefore, to mitigate and/or obviate the above-mentioned drawback in the manner set forth in the detailed description of the preferred embodiment.